Different patients react very differently to chemotherapeutic cancer drugs, and are variably susceptible to drug side effects. Many patients are therefore currently not receiving adequate levels of those drugs. A personalized monitoring of toxic drug metabolites would greatly aid physicians to accurately personalize drug dosage. We propose to develop a rapid oral fluid test of a panel of small drug metabolites for personalized diagnostic monitoring during treatment. We will utilize our patented design for a "discontinuous chromatographic capillary flow solid phase assay", The test can be designed both for home self-monitoring by the patient (over-the-counter device) and for use by physicians in clinics (point-of-care). The key features include: (i), highly sensitive detection of small molecule drug metabolites;(ii), an integrated oral fluid collection design that minimizes sample variability in viscosity, pH and contents, and provides sufficient sample backupvolumes for subsequent confirmatory tests;(iii), a user-friendly, low cost and disposable device.